The command `gud_step` on my system is bound to the keys `C-c C-s` and `C-x C-a C-s`. I don't find this command particularly useful and have tried to unbind it by adding the following to my .emacs file:
```
;; Remove 'gud-step' from the global map.
(global-unset-key "\C-x\C-a\C-s")
(global-unset-key "\C-c\C-s")
(add-hook 'gdb-mode-hook
(lambda()
(local-unset-key (kbd "C-x C-a C-s"))))
(add-hook 'gdb-mode-hook
(lambda()
(local-unset-key (kbd "C-c C-s"))))
```
When I `eval-region` and restart my `gud-gdb` session I still get the default behavior. What am I doing wrong?